In recent years, there has been a further demand for increased performance, such as larger size, higher definition, and faster display frequency, has been placed on flat-panel displays represented by liquid-crystal displays and organic electroluminescence (EL) displays which make use of electroluminescence of organic materials.
In particular, development of thin-film transistors (TFTs), which have excellent characteristics as drive circuits of active-matrix display apparatuses, is being rushed. Amidst the demand for the high current driving performance of thin-film transistors, thin-film transistors using crystallized semiconductor thin-films for the active layer have been put into practical use, and, in particular, top gate-structure, low-temperature polysilicon TFTs which have a semiconductor layer crystallized by irradiation with a laser beam such as an excimer laser is widely used as a device which not only has high current performance but also realizes high ON/OFF current ratio and extremely low parasitic capacitance through a self-alignment process and an LDR structure.